Swapping of Variables

1. The Problem with Direct Assignment

If you try to directly assign a = b, you lose the original value of a, because it gets overwritten.

a = 5
b = 6
a = b
b = a       # direct assignment
print(a)    # 6
print(b)    # 6

Now both a and b have the same value (6), and the original value of a is lost.

2. Swapping Using a Temporary Variable

This is the classic method for swapping two numbers.

a = 5
b = 6

temp = a   # store value of a in temp
a = b      # assign value of b to a
b = temp   # assign value of temp (original a) to b

print(a)   # 6
print(b)   # 5

Output:

6
5

✔ Easy to understand

✔ Works for all data types

✘ Uses extra memory (one extra variable)

3. Swapping Without Using a Third Variable

We can swap values using arithmetic operations without a temporary variable.

a = 5
b = 6

a = a + b   # 5 + 6 = 11
b = a - b   # 11 - 6 = 5
a = a - b   # 11 - 5 = 6

print(a)    # 6
print(b)    # 5

Output:

6
5

✔ No extra variable

✘ Works only with numeric types

✘ May cause overflow in some languages (not in Python)

4. Swapping Using XOR Bitwise Operator

The XOR (^) operation can also be used to swap two numbers without using a third variable.

a = 5        # 0101 (in binary)
b = 6        # 0110 (in binary)

a = a ^ b    # 0101 ^ 0110 = 0011  → a = 3
b = a ^ b    # 0011 ^ 0110 = 0101  → b = 5
a = a ^ b    # 0011 ^ 0101 = 0110  → a = 6

print(a)     # 6 (0110)
print(b)     # 5 (0101)

Output:

6
5

✔ No extra variable

✔ Fast for low-level programming

✘ Works only with integers

5. Swapping Using Python’s Tuple Unpacking

Python provides a simple and elegant way to swap values in one line.

a = 5
b = 6

a, b = b, a

print(a)    # 6
print(b)    # 5

Output:

6
5

How it works:

• Python forms a tuple (b, a)
• Then unpacks it back into (a, b)
• This prevents overwriting and works for any data type.

✔ Most readable

✔ Most efficient in Python

✔ No extra memory

✔ Works for all types (numbers, strings, objects, lists, etc.)

Summary